Responsibility in Canary Wharf high-rises is split. Drains and waste pipes inside your individual flat (up to the soil stack) are usually the leaseholder's responsibility. Shared risers, stacks, and the lateral drain running to the public sewer are typically the freeholder or managing agent's responsibility — and many blocks have a maintenance contract with a drainage contractor on top of that. Beyond the property boundary, the Thames Water-adopted sewer takes over. If you're unsure, we can do a quick CCTV check to confirm where the blockage actually is, and provide a written report you can share with your managing agent if costs need to be apportioned.